A floating sword, aka gravity sword, aka contact sword is a juggling prop that is weighted specifically to allow moves that appear to defy gravity. The majority of the prop's weight is below the gripping point at the pommel of the sword, so that it's balance point is in the middle of the handle (note how the prop balances on a beer bottle in the title photo). I'll include a video of me playing with this one so you get the rough idea.
You know what a light saber is. This instructable will be useful for making regular old lightsabers also, but there is already a ton of information available on that topic all over the internet.
For this build I used very inexpensive electronics from ebay - you could easily incorporate super high output LEDs and high end batteries; for this build I was trying to stick to a very strict budget.
Build cost for this, for me was under $50, but to be fair I already had a number of the components. With some imagination and some scrounging you should be able to do this pretty inexpensively as well.
Step 1: Step 1 - Materials
The tubing I used for the blade is a 32" length of 1" OD x 3/4" ID polycarbonate tubing that I bought from amazon, at about $30 for 6 feet (enough for two sabers). It is also available with many other options like frosting, tinting, etc. from thecustomsabershop.com. You can also use thinner wall material if you want a lighter prop - the 1/8" wall is recommended if you plan on battling your friends with it.
Theblade tipis from thecustomsabershop.com for $5.50 at the time I bought it. Make sure you get the right tip for the tubing you use.
To diffuse the light evenly along the blade, you need some kind of film or treatment. There are many ways to do this, from frosted tubing, to fiber optics to phosphorescent coatings... I chose the cheapest method that appears to yield good results, which is to roll up somecellophane wrapping paperin the middle of the tube to refract the light down the center instead of just letting it all out the sides.
This is a huge can of worms, upon which there is a vast amount of information available. Some saber builders have done amazing things with ultra high output emitters, but I just wanted something that would produce enough light to look cool in the dark, not necessarily rival the sun, so I used:
- A Cheap 3w red LED from eBay (about $1) on a star heat sink.
- A collimating lens that narrows the viewing angle to 8 degrees (also about $1 on ebay)
- A 1000mA constant current driver (also from ebay - about 2 bucks).
Note: pictured above you can see I also tested a green emitter; green LEDs are more efficient than red, and are brighter to your eye even at the same output, however I wanted red for this build so I took the performance hit.
I happened to have several dozen used 18650 lithium ion batteries laying around. The driver board I used needs between 5 and 30 volts to work, so I put two batteries in series (2x3.7v nominal = 7.4v) and called it a day. There are many, many ways you could power this, depending on what you have available, that's small enough to fit inside your handle. 18650 batteries are just under 3/4" in diameter and so worked perfectly inside my handle tubing.
I used button switch from a cheap led flashlightthat happened to be the exact diameter of my handle tubing. This simplified my wiring and kept there from being any irregularities in the round handle, which is important for the contact rolling moves I wanted this prop for.
For the handle itself I used 1" OD aluminum tubingfor the handle itself, and some1" ID x 1.25 OD aluminum pipeas a coupling to connect the 1" OD blade tubing with the 1" OD handle, without creating a large bump along the length of the prop - remember the idea here is to keep it as much like a long smooth cylinder as possible for the rolling moves.
The heavy pommel is what makes this a floating sword. Commercial props sometimes use a steel ball, but I don't have machining facilities to put a bolt hole in one. You could use a bunch of big washers around a bolt screwed into the end - I usedlead sheet that I cut to 2" wide tape and wrapped in several layers around the end until the balance point was where I wanted it to be.
OTHER ODDS & ENDS
I improvised the battery retainer and so on, reusing some of the other parts from the flashlight I cannibalized, and a small PVC fitting. I also used some rivets, tape, glue, grip tape, foam tape, fiberglass cloth and epoxy resin. I will cover this in detail later on, but I will imagine anyone else making this will probably do things at least a little bit differently.
Step 2: Step 2: Assemble the Handle and Blade Coupling
The first thing I did, because it had the most stuff to figure out in it, was to make the handle part. The handle has to hold your batteries, switch, grip, counterweight, and couple to the blade portion of the prop, so I wanted to get it going early and give myself time to scratch my head over the details as I went along.
I missed some detailed photos on these steps, but they are very simple and go something like this:
- Cut the 15" length of 1" OD tubing - note: it's advisable to cut this 1" too long at this point.
- Deburr the tube, and mark it at 1" from the cleaned up end
- Apply grease or anti-seize compound as a lubricant to the OD of the end of the tube.
- Using a dead-blow mallet, carefully hammer the 1" OD tube into the end of the 1" ID tube until it reaches the mark you made on the smaller tube. During this process be very careful to keep the axes of the two tubes aligned - the metal is fragile and can be bent. Don't get over-zealous with your hammer or you will buckle the handle.
- At this point you will likely have damaged the end of the handle tubing with the mallet, so you'll be happy you left an extra inch in step one. You can now trim this off. I like to use some duct tape as a cutting guide to get square cuts - a miter box also works.
- Cut the 1.25" OD tube down to its final length. I wanted a bit of style to it so I put a 45 degree cut. The measurements of this are 2" on the short side and 3.25" on the long side.
- Place your coupling in a vice, and use the top of the jaws as a cutting guide to put a lengthwise cut in the coupling. I also drilled a 3/8" hole at the root of this lengthwise cut. The idea here is to make the blade end of the coupling more flexible than the handle end, so I can get the weaker polycarbonate to slide in without it buckling.
Step 3: Step 3 - Assemble the Tail Switch
This step, of all steps, I imagine the most people will want to do differently than I did. I happen to have a lot of composite materials just laying about, so this made sense for me to do, but I can think of other, easier ways to make a switch. Having said that;
Flashlights are wired such that the body of the flashlight is battery negative, and the button switch in the tail cap of the flashlight just connects the body of the flashlight to the actual battery. This simplifies wiring, as you then just need to connect the lamp to the body and to battery positive.
The easiest way I could think of to get a threaded flashlight tail cap, complete with switch, to work with my saber, was just to stick the back half of a flashlight on the end of the tube. I accomplished this by cutting the flashlight body in half, and then wrapping epoxy/fiberglass composite around that to make it all one piece. Detailed instructions below:
- Cut Flashlight in half (Photo 1)
- Mock flashlight up with handle tube using some internal brace (I used a slightly smaller tube to hold it nicely)
- Assemble your composite materials and mix up your resin.
- Carefully wrap your fiberglass cloth, wetting out with epoxy as you go.
- [Optional] Using teflon tape, apply an over-wrap to the still-wet epoxy composite. This will squeeze out excess resin, and give you a nice tight layup.
- Sand off the teflon tape.
Step 4: Step 4: Start on Your Blade
At this point I wanted to be able to start testing things as I went, so I needed the LED and power supply stuff wired up and assembled. I also wanted to start making sure the light source and diffusion film and so on were going to look OK in case I needed to change course, so it's as good a time as any to start making the blade.
- Cut your polycarbonate tubing to your desired length - mine is cut at 32"
- Deburr, and sand the cut end of your tubing.
- Push a small square of cloth, paper towel, or something through the tubing to pick up any dust and debris - you want the inside of your blade to be clean of foreign debris or it will show up when you put your film in.
- Unroll some cellophane wrapping paper a few inches longer than your blade and cut it as squarely as you can.
- Wipe the cellophane with a tack cloth.
- Note - it's advisable to do this in a very clean area to minimize dust, pet hair, etc.
- Roll your cellophane up so that the axis of the tube you make is the long ways.
- My cellophane is only 30" wide, so if you roll it up the wrong direction it won't be long enough.
- Try to make sure your roll is "square" rather than at an angle, or helix. If your cellophane rolls up in a spiral, gently tap the end so the edges are all flush, or unroll and start again.
- Using your pinky finger, carefully tighten the cellophane roll until it's smaller than the ID of your blade tubing.
- Take care to keep the roll from becoming a spiral while you do this.
- You may not be able to remove your finger once you get it small enough - don't worry, you'll get it back, just hang on a minute.
- Slide the cellophane into the blade until it protrudes from both ends, then carefully unwind your finger so the roll expands to fill the tube. Make sure the roll stays mostly non-spiraled, and your finger should be released.
- Slide the cellophane back out a little ways so that there is room at one end to insert your blade tip. Place the blade tip in but do not glue it in place. You're just trying to get the cellophane placed right at this point. Mark the cellophane at the other end of the tube.
- Pull the cellophane out a few inches, and cut the roll off with a sharp pair of scissors about 1/2"-3/4" shorter than the mark you made. Remember this end of the blade will be hidden by the coupling, and you want a little bit of room to put your LED inside the tube still.
Step 5: Step 5 - Assemble Your LED and Circuit
I know it seems like I'm jumping around a lot here, but there is a method to this madness. Also it goes without saying that it pays to test your circuits at every step so you don't get too far and realize something doesn't work.
- If your LED is not already on a star, install it on one. These standard heat sinks are a necessity if you want your LED to last any amount of time. The LEDs I used are relatively pedestrian 3W units but they definitely generate enough heat to require sinking. If you're using a sweet tri-cree or something, you will need an even larger sink. It's recommended to use thermal compound between the back of the LED and the star base when you do this.
- Solder wire leads to your LED
- To make the collimating lens a snug fit inside the blade tube, I wrapped it in white vinyl tape until it was the exact diameter to require just a bit of force to fit.
- Place your taped up collimating lens over the LED. The ones I used sort of snap in place which is nice and convenient; I also epoxied it on just to be sure.
- Solder your wire leads to your driver board, and wrap your driver board in electrical tape to prevent any shorts inside the metal tube it will live inside of.
- Cram your LED assembly into the base of your blade tube, and move on to the next step, where things start getting exciting.
- I did not use any kind of adhesive to hold the LED assembly to the base of the blade, but I would recommend it, as there's not much way to get at it to fix it later if it becomes dislodged.
Step 6: Step 6: Assemble Your Blade to Your Handle
Alright, things are starting to look rather light-saber-ish at this point! It's a good idea to test your electronics, as after this it gets significantly more difficult to access them.
- Test your LED and driver board.
- Mount the handle in a vise as shown - so that the coupling rests against the side of the vice. This way you don't have to squeeze your handle and potentially damage it.
- Thread your wires through the handle tube so that your wiring comes out the bottom - every wiring step from here on has to be done from the bottom, so make sure you're ready before you get out your mallet.
- Carefully tap the polycarbonate blade tube into the coupling on the end of your handle. Polycarbonate is extremely tough, but if you hit it too hard you can buckle it, leaving permanent crease marks or stress fractures in it.
- As you're doing this, the star base of your LED will get pushed up against the end of the 1" OD handle tube inside your coupling. This is OK, but it's another good reason not to use too much force.
- It would be beneficial to put some kind of heat sink inside the handle tube here for the star to rest against - I did not do this for simplicity and weight reasons.
- You may also wish to put a set screw or adhesive on your coupling for added strength - I haven't had any issues yet with it just being a tight fit however.
- Once the blade is fully seated as seen through the slots you cut earlier, go ahead and glue your blade tip on.
- I used acrylic solvent cement as I figured it would be stronger, but it's quite messy to work with. Many people recommend using a cyanoacrylate instant adhesive like superglue.
Step 7: Step 7: Rig Up Your Batteries
As I mentioned earlier in the instructable, I had some 18650 Lithium Ion cells laying about that I wanted to use. The driver board for the LED is happy as long as it gets between 5 and 30 volts; two (3.7v nominal) lithium cells in series will give me 7.4v nominal to work with. It would work to just put two cylindrical cells in with the (+) end of one touching the (-) end of the other, like in most flashlights, but I wanted to eliminate as much potential movement within the handle as I could, so I actually soldered two cells (+) to (-) and then taped them up.
Now, my flashlight tail cap switch is going to connect battery negative to the handle housing; this means I need to connect the battery (-) terminal on my LED driver to the flashlight housing (See diagram). Unfortunately because I connected the aluminum housing to the handle with epoxy, I don't have an electrical path from there to where the LED is, and I needed to run the battery (-) wire all the way to the flashlight housing to connect it. Lesson learned for next time.
What remains to do is put a plug into the handle tube that is insulated from the handle, but contains a spring contact to make the connection between battery (+) terminal and the LED driver battery (+) terminal. I found that a 1/2" PVC plug was almost exactly the right diameter to slide inside my handle tube. Here is how I made the rest of the battery plug:
- Sand or grind the flange off of your PVC fitting so it will slide into the tube.
- Wrap a few layers of electrical tape around the PVC fitting to make it a snug fit inside the tube.
- Take apart the rest of your cheap flashlight and salvage the battery (+) connection from it.
- In mine, the battery spring was soldered right to the PCB that hosted the flashlight's LEDs, so the LEDs needed to be removed.
- Rough up your PVC and your PCB with some sandpaper and epoxy them together as shown. Once the epoxy cures, sand/grind off any excess PCB around the edges so the assembly still slides into your handle tube.
- Drill a small hole through the plug for your (+) wire, and grind a slot into the side of your plastic plug for the (-) wire.
- You can avoid running the (-) wire in this way if your handle is continuously conductive from where the LED is to the switch - you would just connect your battery (-) wire to the handle housing up near the blade instead of at the switch.
- Poke your your (+) wire through the hole in your plug and solder it to one of the contacts connected to the spring (or just solder to the spring directly). Test your connections before going further.
- With your (-) wire hanging out of the end, insert your plastic plug into the handle tube, with the (-) wire going through the slot in the side of your plug.
- You want the plug to be somewhat difficult to move inside the handle so it doesn't get away from you.
- Make sure you keep hold of the (-) wire so it doesn't get pulled along with your plug as you push it in.
- Using some sort of implement carefully push the plug into the handle, checking your batteries for fitment every so often. Don't push it in too far, or you'll have a very unfortunate problem on your hands.
- Once your (+) plug is in the correct spot, carefully drill through the side of the handle, and into your plastic plug; rivet or glue it in place through the side of the handle tube. Test your connections again to make sure you didn't break a wire with your drill bit.
- At this point the only thing you are missing is the LED driver (-) connection to the flashlight housing. I got excited and channeled my inner kludge monster at this point and just stripped the wire and made sure it got trapped in the threads when I screwed the tail cap on. I intend to improve this at some point, but it actually works pretty well this way.
Step 8: Step 8: Counterweight, Grip Tape, and Padding
At this point you have a working light saber that you may want to run around and play with; in which case go nuts! The whole point for me was making one that I could do contact moves with though, so this step is vital.
DISCLAIMER: In case you're unawares, lead is toxic. It makes an excellent weight because it's extremely dense, and easy to form into whatever shape you want, but it is notoriously bad for humans - wash your hands, and perhaps read up on the negative effects lead can have on your health before you proceed. My design fully encapsulates the lead in a silicone sheath, so it will be contained, but you still have to work with it. If in doubt, use steel or brass, or some other material to make your counterweight.
- The first thing I needed to do was to cut my 4" wide lead sheet in half to make a 2" wide by 36" long strip. Ordinary household scissors work just fine for this but should be carefully cleaned or discarded afterwards.
You may want to play with how much lead you use to adjust where the balance point of the prop is. This amount with the materials I used put the balance point halfway between the blade and the pommel end.
- Tape the end of your lead strip to the handle, and start applying silicone adhesive.
- I used DOW 732 because it's awesome, but I'm sure any old silicone would be fine.
- Make sure to get a nice even, thin coat, wrapping the lead around as you go, so each layer gets glued to the layer below it.
- Once you have the whole strip rolled around the hilt, gently twist your rolled up lead to tighten the wrapping and squeeze out any excess silicone. Using your finger, smear silicone all over the outside of the lead and the edges to prevent contact between lead and the outside world.
- Optional: Using weatherstripping or insulating duct tape, build up a contour on the handle, and over-wrap the lead weight to provide a little bit of padding - it's no fun to catch an un-padded lead weight in the face if you mess up a move. A little bit of padding goes a very long way. A layer of tightly wrapped electrical tape over top of your foam tape will hold it firmly in place and give you a nice even black pommel.
- Apply grip tape - this is pretty self explanatory.
- I used baseball bat grip because I was in a rush. I don't like this stuff because its kind of overpriced for what you get.
- Tennis racket over-grip works too, and is pretty easy to find; there are many long winded discussions online to be found about what works best; whatever you use will probably come with instructions.
- Optional: Mark the balance point.
- This is very useful for performing rapid visual calculations while you're spinning the prop around. It's very helpful to be able to look at an airborne prop and visually locate the center of mass so you can catch it exactly where you need to.
- For this, I used white vinyl marking tape - white electrical tape would be an excellent alternative.
Step 9: Step 9: Practice
For me the whole point of this prop was to have something to practice with that was entertaining without being dangerous (normally I spin a fire sword), so the practice part is sort of implied. I find this prop to have a fairly high level of difficulty, but I'll jump to reassure anyone reading that I've never been particularly coordinated, and if *I* can do it, you probably can with enough practice. Enjoy playing!